1. Field of the Invention
This invention relates to a sound effect-creating device used in electronic musical instruments and the like, and more particularly to a sound effect-creating device comprising signal-modulating means, a plurality of signal-delaying means, and signal-mixing means, a combination of which can be freely selected by a player for operating the device, to thereby impart, to original musical sounds to be created by his or her performance, a so-called ensemble effect comprising various effects including the chorus effect which gives his or her listeners the impression that they were listening to music played by a plurality of players.
2. Prior Art
In electronic musical instruments, such as electronic pianos and other electronic keyboard instruments, an artificial musical sound in an audio frequency range, which corresponds to a key of the keyboard selectively depressed by a player, is synthesized by electronic computation. In such electronic synthesis, the artificial musical sound is not only synthesized in a desired tone color and tone quality, but also often imparted with various sound effects produced according to settings selectively made for control thereof by the player via switches, volume knobs, and the like of the instrument. The ensemble effect includes a so-called chorus effect, i.e. the effect of making one player's listeners feel as if they were listening to music played by a plurality of players, as well as the vibrato effect of giving slight and rapid vibrations in pitch. As a result, the listeners can feel as if they were present in a concert hall, listening to music played by a plurality of players. Therefore, in the field of the electronic musical instruments, how to realize the ensemble effect is a very important technique in designing an instrument.
FIG. 1 shows a conventional sound effect-creating device which is adapted to artificially impart such sound effects to an artificial musical sound produced by an electronic musical instrument. In the figure, a sound effect-creating device generally designated by reference numeral 71 has frequency modulators 72, 73 and 74. These frequency modulators are supplied via respective signal input terminals 72a, 73a and 74a with a signal artificially synthesized by means therefor, not shown, which is representative of an artificial musical sound to be produced by the electronic musical instrument. This signal before modification for imparting the artificial sound effects to the artificial musical sound will be hereinafter referred to as "the original sound signal". The frequency modulators are supplied, via respective modulating signal input terminals 72b, 73b, and 74b thereof, with modulating signals each having a frequency of 5 Hz and being shifted in phase by 120 degrees from each other, which are also synthesized by means therefor, not shown. Further, these frequency modulators 72, 73, and 74 have output terminals 72c, 73c, and 74c connected to input terminals 75a, 75b, 75c of a mixer 75, respectively. The mixer 75 has an output terminal 75d connected to an arithmetic unit, not shown.
According to this sound effect-creating device 71, the original sound signal is supplied via the signal input terminals 72a, 73a, 74a to the frequency modulators 72, 73, and 74, separately and simultaneously, where the input signals are separately frequency-modulated by the modulating signals input via the modulating signal input terminals 72b, 73b, and 74b, respectively. The resulting modulation signals are supplied to the mixer 75, where they are added up to form a mixed signal. In this case, through the above frequency modulations, each modulation signal has a swell having a frequency of 5 Hz. Further, the frequency modulations are effected by the respective modulating signals different in phase from each other by 120 degrees, so that the resulting modulation signals interfere with each other when they are added up by the mixer 75, to produce a lot of mutual modulation components. As a result, the resulting mixed modulation signal is in such a modified form that it will realize the ensemble effect consisting of the vibrato effect of giving vibrations to a musical sound through swell of the frequency of the resulting signal and the chorus effect of making one player's listeners feel as if they were listening to music played by a plurality of player, which is effected through the many mutual modulation components of the signal.
However, such a conventional sound effect-creating device suffers from the following inconveniences: First, since provision of a plurality of frequency modulators is required, the circuit configuration of the device is complicated. Particularly with a sound effect-creating device of a digital type, when an encoded original sound signal is frequency-modulated by a digital circuit, it is required to shift the phase of a clock used in selecting addresses storing data of the encoded original sound signal. This results in a technically difficult requirement of substantially increasing the frequency of the clock to perform high-speed computation. Moreover, the use of a plurality of frequency modulation circuits as described above requires parallel processing of data, and hence it is required to use a computer having high-speed processing capability in order to control the whole frequency modulation circuits, and at the same time to employ a complicated processing method.
Further, although the produced sound effects per se include the vibrato effect and the chorus effect, they are merely based on different phases of the modulating signals and hence even with the presence of a plurality of signal components resulting from the artificial diversification described above, the intervals of time between the components are not long enough to produce a sufficiently deep chorus effect. Further, they cannot give the listeners a sufficient degree of the sense of spread of sound for them to enjoy the sense of concert hall presence.